The present invention relates to a position indicating control apparatus, and particularly to such apparatus of the type which is commonly referred to as a "mouse".
A mouse is a pointing device, typically for use with visual display systems in which a transducer converts translational motion of a housing into a position signal for controlling movement of a cursor associated with a visual display system. The mouse moves over a passive surface, such as a sheet of paper on a desk top, this two-dimensional motion corresponding directly with the two-dimensional motion of a cursor in a graphic display.
Electronic mice are of fundamentally two types viz., mechanical and optical. A mechanical mouse comprises one or more rotatable elements which frictionally engage the underlying paper or support surface. The components of rotation of these rotating elements along two orthogonal axes are sensed by transducers which generate electrical signals indicative of the motion. An optical mouse has no moving parts. It moves over an array of indicia on a special pad. A lamp in the mouse illuminates the indicia, the reflected image being sensed by a transducer which generates position-indicating electrical signals.
The present invention relates to an improved form of mechanical mouse, and particularly to the type of mechanical mouse which utilizes a universally rotatable ball as the rotatable element. Typically, the ball sits in an aperture in the base of the mouse housing, so that a portion of the ball projects through the aperture for frictional engagement with the underlying support surface. Such a mouse is disclosed, for example, in U.S. Pat. Nos. 3,987,685 and 3,835,464. In such prior mechanical mice, a plurality of rotatable members frictionally engage the ball at points around its equator and adjacent to its top for cooperation with the base to hold the ball in position over the aperture. At least two of these rotatable members serve as sensors to detect the components of rotation of the ball. The prior devices have typically required complex mounting structure to mount these multiple rotating members. In those cases, such as in U.S. Pat. No. 3,987,685, where the rotating members include elongated shafts, expensive bearings have been provided for the shafts. These prior mouse assemblies are quite expensive, both because of the large number of expensive parts which are used, and because of the time and labor-consuming assembly required.